The disclosure concerns a valve device, and a damping device.
Modern slip-controllable vehicle braking systems offer additional functions which support the driver for example in maintaining the distance from a preceding vehicle. This is achieved by active intervention of the braking system, in that this builds up a brake pressure at the wheel brakes without the driver himself activating the brake pedal. To ensure that the driver does not perceive any disruptive noise during this process, damping devices are used which reduce pressure pulsations caused by the pressure generators of the braking system.
These damping devices consist of a hydraulic resistance and a hydraulic capacitance which is connected upstream of the hydraulic resistance in the hydraulic circuit. A high throttling effect of the hydraulic resistance is necessary for the efficacy of the damping device.
However, a high hydraulic resistance has the disadvantage that it causes a large pressure fall. As a result, the load on the drive of the pressure generator concerned rises and its delivery capacity falls. Finally, this causes a deterioration in the pressure build-up dynamics of the braking system.
As a counter-measure, it is known to use hydraulic resistances with flow-dependently adjustable throttle cross-sections. Large volume flows increase the throttle cross-section of such resistances and reduce the pressure fall. Such hydraulic resistances may be formed for example as valve devices, the valve element of which executes a stroke depending on the throughflow or the prevailing pressure conditions.
DE 40 28 941 A1 describes a valve device which is used as an outlet valve on a stroke piston pump of a vehicle braking system, and which comprises a valve body (pump cylinder) with a throttle cross-section formed thereon, and a valve element regulating the throttle cross-section. The valve element is pressed by a return spring against a valve seat surrounding the throttle cross-section and closes this if the mechanical force of the return spring on the valve element is greater than the hydraulic forces from the pressure medium delivery which support its opening. Under hydraulic forces which are higher than the mechanical return forces, the valve element executes a stroke depending on the force difference, lifts away from the valve seat and opens a control cross-section through which pressure medium can flow past the valve element to an outflow of the valve device.
Viewed in the flow direction of the known valve device, this outflow is arranged laterally on the valve body so that the outflowing pressure medium is deflected into the valve body. Because of this deflection of the pressure medium, flow-induced radial or transverse forces act on the valve element. The opening movement of the valve element consequently resembles a rocking motion, wherein the valve element moves away from the opening of the outflow in the valve body and in some cases rests on the region of the wall of the valve body lying opposite the outflow. The transverse forces on the valve element prevent exclusively centering forces from acting on the valve element, which would excite the valve element to axial oscillations and generate noise.
The disadvantage is that a valve device with a laterally arranged outflow is more complex to produce, and because of the pressure medium deflection, reacts more sensitively to fluctuations in viscosity of the pressure medium, and hence has a wider spread of throttle properties, than valve devices in which the inlet and outlet lie axially opposite each other.